[GRASS-user] t.rast.algebra with strds of different granularity

[Veronica Andreo]

Hi list,

Just by mistake, I did an operation between two time series (strds) with
t.rast.algebra, and only after a while I realized that they have different
granularity (while I thought they had the same). One of them is daily (from
00:00:00 to 00:00:00, 24 hs intervals) and the other is also daily, but
intervals are from 10:30 to 22:30 (12 hours). Anyway, the second one is
temporally included/contained in the first one. However, when I make a
substraction among them, I get an empty strds as result and no error nor
warning message.

This is how I wrote the command:

t.rast.algebra -n basename=lwr_minus_orig expression="abs_lwr_minus_orig =
abs(LST_Day_2016_lwr1 - LST_Day_2016_orig)"

How should it look like for the temporal topology to be considered, then?
Something like:

expression="abs_lwr_minus_orig = abs(LST_Day_2016_lwr1 { -, contains }
LST_Day_2016_orig)"  ??

Shouldn't a warning be raised when granularities are different and no
temporal topology operator is used? Dunno if that's possible at all.

Thanks for any tips

Vero
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